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We Know Kids
The Willows Pediatrics Blog

COVID 19 Testing: Antibody and Viral tests

There are two kinds of tests for COVID-19: a viral test and an antibody test.

  • A viral test (nasal or oral swab) tells you if you have a current infection
  • An antibody test (blood test) tells you if had a previous infection

Viral Tests: Testing for current infection

To learn if you have a current infection, viral tests are used. A viral test is collected by a nasal or oral swab at a testing center in our area.

Who should be tested?

  • The decision to get tested depends on several different factors including how sick the patient is, what medical problems the patient has and who resides in the patient’s household (e.g. an immunosuppressed family member, a parent who is a health care worker)
  • At this time, we still encourage testing only if you have symptoms suggesting a COVID-19 infection.
  • If you have symptoms suggesting COVID-19 and want to get tested, please call our office.
  • If you have gotten tested and are awaiting the results, please isolate/quarantine to avoid possibly spreading the infection to others.

Interpreting the results

  • If you test NEGATIVE for COVID-19 by a viral test while you have symptoms, then you likely do NOT have COVID-19. Though we know that there are some false negatives, meaning people who actually DO have COVID but get a negative test result, a false negative result is unlikely.
  • If you test POSITIVE for COVID-19 by a viral test then you have an active infection. Please quarantine in your home and isolate as much as possible from others in your home. If you test positive, we can discuss with you how to minimize spread within your home and when you can safely leave isolation.

Antibody Tests: Testing for past infection

Antibody tests are blood tests that check if your body has antibodies from a previous infection with the virus. Antibodies are proteins our immune system makes when we are exposed to a virus and continue to circulate in our blood after we have recovered from the infection. COVID-19 antibody tests cannot be used to see if you have a current infection, as sometimes the antibodies cannot be detected for weeks after the initial infection.

We use antibody testing for many other diseases to tell us if a patient has had an infection or has immunity to a disease. For diseases that have been studied over time we know what level of antibody is effective and we know whether that antibody can give you temporary or permanent immunity. However, since COVID-19 is a new disease we don’t have all the facts yet.

Cautions regarding antibody tests:

  • We do not know at this time if antibodies provide immunity against getting re-infected
  • We do not know how specific the antibody tests are for detecting antibodies to SARS-CoV-2 versus closely related coronaviruses such as the common cold.
  • There are many tests available right now but few of them have been FDA approved, meaning we do not know how accurate these tests are. In other words, if the test says you have antibodies, or don’t have antibodies, how likely is that to be true?

Given all of these cautions, we are not currently recommending antibody testing for most people. The only scenario in which we DO recommend testing is if you have had a positive COVID-19 viral test and are interested in plasma donation.

Why we don’t think you should get an antibody test now:

  • We are concerned that you may get a “positive” result when you don’t actually have antibodies to COVID. This could happen because these tests are still very new, they were released to the market before the FDA validated them and you may have very similar antibodies from a very similar virus you’ve had in the past. If you got a positive result you may interpret that to mean you are immune, when in fact you are not. This could be dangerous as you may not be as rigorous about wearing a mask or social distancing and accidentally expose yourself or others.
  • We don’t know yet what having antibodies to COVID-19 means. We don’t know if those antibodies confer immunity and, if so, how long that immunity lasts.
  • Antibody tests are usually expensive. Since many of the tests on the market are not FDA approved they may not be covered by insurance.
  • Antibody tests require a blood draw in a doctor’s office or hospital. We usually do everything we can to minimize blood draws in kids to avoid discomfort.

Looking forward:

The scientific community is working furiously to learn more about COVID-19 each and every day. We are hopeful that soon we will know more about COVID-19 antibodies and immunity. We are also hopeful that the FDA will review the tests on the market and guide us to which tests are the most accurate. We will continue to follow this issue closely to give you the best guidance and we will update you when our recommendations change.

For now, please continue to social distance, stay home if you or anyone you’ve been in contact with is sick, and wear a mask when social distancing is not possible.

Sources and Suggested Reading

https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html

https://www.scientificamerican.com/article/what-covid-19-antibody-tests-can-and-cannot-tell-us/

https://www.idsociety.org/news–publications-new/articles/2020/emphasizing-need-for-more-information-idsa-releases-antibody-testing-primer2/